Use knot mod-geoip for nextnode address

Use mod-geoip with the mode: subnet

https://www.knot-dns.cz/docs/2.9/html/modules.html?highlight=subnet#mod-geoip-config-file

changed milestone to %DNS

added DNS Knot DNS labels

mentioned in merge request !528 (merged)

created merge request !528 (merged) to address this issue

added Doing label

closed via merge request !528 (merged)

removed Doing label